1. Field of the Invention
The present invention relates to a fan housing and, more particularly, to a housing for an axial-flow fan including stationary blades.
2. Description of the Related Art
Currently, most impellers for heat-dissipating fans on the market include plural rotary blades evenly spaced around hubs of the impellers. Since the rotary blades of an impeller are spaced with equal intervals, angles between radially extending directions of any two adjacent rotary blades are identical. Thus, while the impeller is turning, a pure-tone noise is easily arisen and then transmitted in the air.
In order to solve the problem mentioned above, Taiwan Patent Application No. 97132907 entitled “HEAT-DISSIPATING FAN” discloses an impeller with various angles between any two adjacent rotary blades. When air flows are discharged from the impeller, noises with the same tone are not easily arisen, which leads to a decrease in the intensity of pure-tone noise. However, owing to the situation of different angles between any two adjacent rotary blades, which leads to a structural imbalance, the difficulty of a rotation-balance adjustment therefore increases. Also, it is necessary to correct the pitch or yaw of each rotary blade or to conduct dynamic balancing test, and, thus, cost is increased for the need of extra manpower. Besides, a conventional housing for an axial-flow fan commonly has a plurality of stationary blades, but manufacturers haven't known how to minimize pure-tone noise by different designs of the stationary blades.
Taiwan Patent Issue No. 488497 entitled “PRESSURE-INCREASING AND AIR-GUIDING FOR FAN” discloses a fan housing with stationary blades and is shown in FIG. 1. Referring to FIG. 1, a conventional fan housing 90 includes a frame 91, a base 92 received in the frame 91 and for an impeller 93 to be mounted on, and an air-guiding unit 94 constructed by plural stationary blades 941, The stationary blades 941 are fixed between the base 92 and the frame 91. By the arrangement of the stationary blades 941 radially attaching to the base 92, the stationary blades 941 are able to guide airflow generated from rotation of the impeller 93 to enhance air pressure.
Although the air pressure can be enhanced by the stationary blades 941, noises with the same tone forming pure-tone noise will arise due to the stationary blades 941 being spaced with identical intervals and identical angles between any two adjacent stationary blades 941. Hence, there is a need for an improvement over the conventional fan housing 90.
Moreover, Taiwan Patent Issue No. I276743 entitled “FAN AND FAN HOUSING WITH AIR-GUIDING STATIC BLADES” discloses a fan housing including a frame and plural stationary blades spaced evenly. Furthermore, an airflow-guiding element that is wing-shaped is arranged between any two adjacent stationary blades and formed on an inner periphery of the frame. Thus, with the arrangement of the airflow-guiding elements disposed beside the stationary blades, turbulence is restrained on the surfaces of the stationary blades to reduce noise arising from the turbulence. However, owing to the airflow-guiding elements extending from the inner periphery of the frame, difficulty in forming the fan housing is caused, and manufacturing cost is increased.
Additionally, Taiwan Patent Issue No. M287387 entitled “FAN AND FAN HOUSING WITH AIR-GUIDING STATIC BLADES” discloses a fan housing including a frame and plural stationary blades fixed and spaced evenly inside the frame. At least one airflow-guiding element is mounted on each stationary blade and along the circumference of the stationary blade. Thus, when an impeller in the fan housing rotates to generate airflow, the airflow-guiding elements can guide the airflow to restrain turbulence on the stationary blades from arising noise. However, difficulty in forming the fan housing and increased manufacturing cost will result from each stationary blade having at least one airflow-guiding element extending thereon.
As has been discussed above, since rotary blades of an impeller are spaced evenly and angles between any two adjacent rotary blades are the same, pure-tone noise easily arises while the impeller is turning. Although the above conventional impeller disclosing different angles between any two adjacent rotary blades overcomes the problem of pure-tone noise, difficulty in correcting the pitch or yaw of each rotary blade and dynamic balance of the impeller results in a wobbling impeller, and, then, related components will be damaged after a long-term operation. Besides, an impeller commonly mounted in the conventional fan housing has a plurality of stationary blades spaced evenly, but nobody has modified the structure of the stationary blades to overcome the problem of pure-tone noise. Hence, there is a need for an improvement over the conventional fan housing.